This invention relates generally to scraper arrangements for conveyor belts and particularly is concerned with apparatus for biasing scrapers into contact with a conveyor belt surface at a location which is adjacent, near or on a head pulley.
A primary belt scraper or, more generally, a scraper at a head pulley of a conveyor belt, may be called upon to exert a substantial scraping action. To achieve this objective the scraper must be biased into scraping engagement with the conveyor belt surface which is to be cleaned, with a fair amount of force but in such a way that the scraper is deflectable, away from the belt, by significant obstructions on the belt.
The biasing arrangement which is adopted should be capable of being reset, from time to time, to compensate for wear on the scraper due to use. It is also desirable to be able to mount the scraper in different orientations to take account of different operative requirements
U.S. Pat. No. 5,992,614 relates to a tensioning device which enables an adjustable force to be exerted on a shaft which supports a scraper blade. A spring is used to provide a resilient force applying mechanism.
The spring is not self-dampening and is exposed and hence is subject to corrosion. Another factor is that a scraper blade is mounted directly to the shaft in a fixed orientation. A variation of this arrangement is shown in PCT/ZA98/19863.
EPO 583 731 shows a basic arrangement, which has a similar effect to the device of U.S. Pat. No. 5,992,614, but wherein the biasing force is generated by twisting a resilient tube about its axis. Different mounting configurations are shown, but there is no positional adjustment facility. EPO 497 324 shows a similar arrangement.
According to one aspect of the invention there is provided a scraper arrangement for use with a conveyor belt which includes an elongate member to which at least one scraper blade is mounted, a support for the elongate member which allows at least limited rotation of the elongate member relatively to the conveyor belt with the scraper blade in scraping engagement with the belt, a tubular component which is mounted for at least limited rotation relatively to the elongate member, at least one resiliently deformable torsion element, at least partly inside the tubular component, means for retaining the tubular component at a selected angular orientation with the torsion element in a deformed state characterised therein that the tubular component has an angular inner surface, an angular extension member is located at least partly inside the tubular component and the torsion element acts between the angular inner surface and the extension member.
The torsion element may be located at least partly inside the tubular component bearing against a surface or surfaces of the extension member which are within the tubular component.
The scraper arrangement may include four torsion elements respectively positioned at four inner corners of the tubular component, bearing respectively against four outer sides of the extension member.
In one form of the invention the scraper arrangement includes a clamp engaged with the elongate member, which permits at least limited rotational adjustment of the scraper blade relatively to the tubular component.
The scraper arrangement may include a mounting bracket whereto the tubular component is mounted for limited sliding adjusting movement relatively to the bracket.
The invention also provides a torsion unit for use with a conveyor belt scraper which includes a tubular component, an extension member which is located at least partly inside the tubular component, at least one resiliently deformable torsion element inside the tubular component, and a flange on the tubular component, characterised therein that the tubular component has an angular inner surface, the extension member is angular and the torsion element acts between opposed surfaces of the angular inner surface and the extension member.
The flange may be located at an end of the tubular component and the extension member may project from the tubular component at this end.
The torsion unit may be provided in combination with a scraper which has an elongate member, at least one scraper blade mounted to the elongate member, and mounting means to fix the elongate member to support structure so that the elongate member is rotatable at least to a limited extent relatively to the support structure, the extension member of the torsion unit being engaged with the elongate member and the combination including means for securing the flange of the torsion unit to the mounting means with the torsion element in a desired state of deformation.
The torsion unit may include a clamp which permits at least limited rotational adjustment of the scraper blade relatively to the torsion unit and the torsion unit may also include a bracket to which the tubular component is mounted so that the tubular component is slidably movable, to a limited extent, relatively to the bracket.